This application is based on Japanese Patent Applications No. 2001-32911 filed on Feb. 8, 2001, No. 2001-34481 filed on Feb. 9, 2001, No. 2001-91002 filed on Mar. 27, 2001, No. 2001-388220 filed on Dec. 20, 2001, and No. 2001-388056 filed on Dec. 20, 2001, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an apparatus for controlling a throttle valve, a method for manufacturing an apparatus for controlling a throttle valve and a motor apparatus.
2. Description of Related Art
If the temperature is cold, the valve of the throttle valve may get a malfunction by an icing. The icing is caused by moisture in the air condensed within the intake pipe and froze on a contact portion among a valve of the throttle valve and an inner wall of the intake pipe.
JP-B-H07-49780 discloses an apparatus for controlling a throttle valve for heating a vicinity of the valve by flowing an engine coolant through a part of a throttle valve housing for preventing it from getting cold. However, according to the arrangement disclosed in the publication, a construction is complex and also the cost may be expansive. Moreover, since the passage of the engine coolant is only arranged on a very little part of a portion of the throttle valve housing that is vicinity of the valve, if the throttle valve housing is made of a low heat conductive resin or the like, it may be difficult to prevent the valve from the icing malfunction.
JP-A-H07-166897 discloses an apparatus for controlling a throttle valve with a motor. The motor is directly provided in a body member for the purpose of improving heat radiation and a vibration resistance. A body member is formed of aluminum and the like in order to reduce its weight and improve its heat radiation, and a bearing holder member is attached to the body member by means of such as screws or machine screws.
However, the above-described attachment of the motor housing and the bearing holder member to the body member by means of the screws or the machine screws undesirably causes the number of parts and the number of assembly processes to be increased, which results in a serious difficulty to decrease the manufacture cost of the entire body of a throttle valve with a motor.
JP-A-H10-317998 discloses an apparatus for controlling a throttle valve. The apparatus has a throttle body having a water passage through which an engine coolant flows. However, the water passage is only contact with a part of a circumference of an intake air passage. Therefore it is difficult to heat the throttle valve body sufficiently. Further, in case of the water passage being formed in the throttle body, it is important to seal water in the passage.
Therefore it is an object of the present invention to provide an apparatus for controlling a throttle valve which is capable of preventing the icing malfunction effectively.
It is another object of the present invention to provide a motor apparatus which is capable of reducing number of parts and manufacturing cost.
It is a further object of the present invention to improve reliability of an apparatus for controlling a throttle valve made of resin.
According to an aspect of the present invention, a yoke of a motor for controlling a throttle valve is exposed to an intake air. Therefore the motor is cooled and a valve is prevented from the icing malfunction.
According to the other aspect of the present invention, a passage through which a heat conductive medium flows is arranged to pass through a vicinity of the motor. Therefore, the heat conductive medium is heated by the motor and the valve is prevented from the icing malfunction.
According to the other aspect of the present invention, a bearing holder member and a body member are made of the same resin and are welded. This arrangement makes it easy to manufacture and reduces number of parts.
According to the other aspect of the present invention, the body member is made of resin and has a passage in which a heat conductive medium flows. In case of the above arrangement, bridge portions are arranged in the passage to strengthen the body member. In case of another arrangement, the body member is formed as a seamless body to provide a reliable seal on the passage. In case of still another arrangement, the body member provides pipes for an intake and an outlet of the passages, which are formed by joining separate parts. This arrangement provides reliable seal on the passage.